Model-data comparisons of shear waves in the nearshore
Noyes, T. James
Guza, R. T.
Herbers, T. H. C.
MetadataShow full item record
Observations of shear waves, alongshore propagating meanders of the mean alongshore current with periods of a few minutes and alongshore wavelengths of a few hundred meters, are compared with model predictions based on numerical solutions of the nonlinear shallow water equations. The model (after Özkan-Haller and Kirby (1999)) assumes alongshore homogeneity and temporally steady wave forcing and neglects wave-current interactions, eddy mixing, and spatial variation of the (nonlinear) bottom drag coefficient. Although the shapes of observed and modeled shear wave velocity spectra differ, and root-mean-square velocity fluctuations agree only to within a factor of about 3, aspects of the cross-shore structure of the observed (∼0.5–1.0 m above the seafloor) and modeled (vertically integrated) shear waves are qualitatively similar. Within the surf zone, where the mean alongshore current (V) is strong and shear waves are energetic, observed and modeled shear wave alongshore phase speeds agree and are close to both V and C lin (the phase speed of linearly unstable modes) consistent with previous results. Farther offshore, where V is weak and observed and modeled shear wave energy levels decay rapidly, modeled and observed C diverge from C lin and are close to the weak alongshore current V. The simulations suggest that the alongshore advection of eddies shed from the strong, sheared flow closer to shore may contribute to the offshore decrease in shear wave phase speeds. Similar to the observations, the modeled cross- and alongshore shear wave velocity fluctuations have approximately equal magnitude, and the modeled vorticity changes sign across the surf zone.
Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 110 (2005): C05019, doi:10.1029/2004JC002541.
Suggested CitationArticle: Noyes, T. James, Guza, R. T., Feddersen, Falk, Elgar, Steve, Herbers, T. H. C., "Model-data comparisons of shear waves in the nearshore", Journal of Geophysical Research 110 (2005): C05019, DOI:10.1029/2004JC002541, https://hdl.handle.net/1912/3669
Showing items related by title, author, creator and subject.
On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number Zhou, Zheyu; Yu, Xiao; Hsu, Tian-Jian; Shi, Fengyan; Geyer, W. Rockwell; Kirby, James T. (John Wiley & Sons, 2017-04-11)The nonhydrostatic surface and terrain-following coastal model NHWAVE is utilized to simulate a continually forced stratified shear flow in a straight channel, which is a generic problem to test the existing nonhydrostatic ...
Ogden, Kelly A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Internal hydraulic jumps in flows with upstream shear are investigated numerically and theoretically. The role of upstream shear has not previously been thoroughly investigated, although it is important in many oceanographic ...
Quantification of the spatial and temporal evolution of stratified shear instabilities at high Reynolds number using quantitative acoustic scattering techniques Fincke, Jonathan R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-02)The spatial and temporal evolution of stratified shear instabilities is quantified in a highly stratified and energetic estuary. The measurements are made using high-resolution acoustic backscatter from an array composed ...